#include <bits/stdc++.h>
using namespace std;

int main() {
	double x;
	cin >> x;
	double l = -100, r = 100;
	while (r - l >= 1e-8) {
		double mid = (l + r) / 2;
		if (mid * mid * mid >= x) {
			r = mid;
		} else {
			l = mid;
		}
	}
	printf("%.6lf\n", l);
	return 0;
}